Week of Feb 15

Wednesday: Review! Spent the first bit talking through PT and Coulomb’s law, then evidence for wave mechanical model. 2nd half of class worked on pages in giant packet.

Thursday: Test

Friday: Started new packet on ionic and metallic bonding. Went over differences in the 3 types of bonding. See today’s notes for help. Also talked about transition metal ions – they lose their 4s first (this is because the 4s energy shell becomes higher in energy than the 3d once you start putting e- in the 3d. The 3d actually shields the 4s electrons. This is hard to understand if you think of electrons in rings, so you’ll need to remember that the 3d are actually in clover shaped orbitals while the 4s is more like a ring! The gist, is that the 3d electrons can be closer to the nucleus than the 4s and therefore shield the 4s. All transition metals have a +2 ion, but often they have more than 1 possible charge because they can also lose d electrons. After about Mn, the transition metals stop losing d electrons because they are too strongly held to the atom. We also looked at changes in radius for ions. Atoms that lose electrons get smaller. Electrons that gain electrons get bigger – this is because of the ratio of protons to electrons. More electrons to protons means a bigger radius. When looking at trends in ionic radius it is best to consider an isoelectronic series (a set of atoms that all have the same electron configuration…e.g. compare ionic radius of ions that react to be like Neon). This way you don’t have to compare what happens when both electrons and protons are changing. See section 9.2-9.3 in textbook.